Methods of polymerizing n-vinyl lactams with a metal oxide or hydroxide and water catalyst



United States Patent METHODS OF POLYMERIZING N-VINYL LAC- TAMS WITH AMETAL OXIDE 0R HYDROXIDE AND WATER CATALYST Frederick Grosser, MidlandPark, and Eugene V. Hort and Arthur Schwartz, Metuchen, N.J., assignorsto General Aniline & Film Corporation, New York, N.Y., a corporation ofDelaware No Drawing. Filed Oct. 23, 1963, Ser. No. 318,204

15 Claims. (Cl. 260-883) The present invention relates, in general, tothe polymerization of N-vinyl lactams and, in particular, to improvedmethods of polymerizing N-vinyl lactams to produce insoluble polymersthereof.

Polymerized N-vinyl lactams and particularly polyvinyl pynrolidone ofthe type that are soluble in water and many common organic solvents arewell known and widely used in industry as stripping agents in processesfor the dyeing of textiles; dispersants in suspension polymerizations;thickening agents for pharmaceuticals, veterinarian and cosmeticpreparations; constituents of adhesive and sizing compositions; bindersfor special lithographic and printing processes and as a modifier orreplacement for gum arabic; gelatin or polyvinyl alcohol. In addition,perhaps the most widely known and most successful use of a polyvinyllactam has been the use of polyvinyl pyrrolidone as a blood plasmacolloid for intravenous use and shock therapy.

Only recently has it been discovered that insoluble polymers of anN-v-inyl lactam, such as N-vinyl pyrrolidone, could be obtained byheating, for example, N- vinyl pyrrolidone at an elevated temperature inthe presence of a small amount of a catalyst consisting essentially of acompound selected from the groups consisting of alkaline metals andalkaline earth metals and their corresponding oxides, hydroxides andalkoxides. The polymerization reaction was initiated by subjecting thereaction charge to high temperatures until the polymerization reactionstarted. The induction times experienced by this procedure were quitelong and the reaction periods varied from about four hours to as much astwenty-four hours. Sometimes as a result of maintaining the reactioncharge at such high temperatures for such relatively long periods,thermal runaways of the reaction were induced. It was also noted thatthe presence of impurities in the starting material affected thepolymerization reaction as well as the purity, color and yield of thefinal product. Thus, special precautions were taken to remove impuritiesfrom the ingredients as well as drying them .and the reaction vessel toeliminate water.

Accordingly, it is an object of this invention to provide methods ofproducing insoluble polymers of N-vinyl lactams.

Another object of this invention resides in provision of catalyticmethods of polymerizing N-vinyl lactams to produce insoluble polymersthereof.

Yet another object of this invention resides in the provision ofimproved catalytic methods of producing insoluble polymers of N-vi-nyllactams wherein the purity of the starting material did not inhibit thepolymerization reaction.

Still another object of this invention resides in the provision of novelcatalytic methods for the polymerization of N-vinyl lactams wherein theinduction period is controlled and/or shortened; permits the use oflower reaction temperatures; increases substantially the yield andquality of the polymer so produced.

Further objects and advantages of the invention will become furtherapparent from the following detailed description thereof.

3,277,066 Patented Oct. 4, 1 966 "Ice It has now been discovered thatsignificant increases in yields of polyvinyl lactams are obtained bymethods which comprise heating a mixture comprising an N-vinyl lactam, apolymerization catalyst, hereinafter more fully described, and water ata first elevated temperature for a period of time suflicient to induceincipient polymerization and forthwith cooling said mixture to a secondtemperature lower than said first temperature and maintaining saidmixture at said second temperature until polymerization is complete.

The amounts of water which have been found useful in achieving theobjects of the invention can vary from as little as 1.0 weight percentand lower to .as much as 70 weight percent based on the weight of the'N-vinyl lactam charged to the reaction vessel. Beneficial results areobtained by employing amounts of water in the range of from 5 weightpercent to about 40 weight percent based on the N-vinyl lactam and is,therefore, preferred. Either distilled or ordinary fresh water may beused.

The N-vinyl lactams which are amenable to the methods of the inventioncan be conveniently characterized by the formula:

wherein each R is independently a member selected from the groupconsisting of hydrogen, methyl and ethyl, R represents a member of thegroup consisting of hydrogen and alkyl groups containing from 1 to 4carbon atoms and n represents a whole positive integer of from 2 through4.

Typical N-vinyl lactams include N-vinyl pyrrolidinone itself,

N-vinyl peperidone, N-vinyl caprolactam, N-vinyl-3-methyl pyrrolidinoneor piperidone, or

caprolactam, N-vinyl-4-methyl pyrrolidinone, or piperidone orcaprolact-am, N-vinyl-S-methyl pyrrolidinone or piperidone,N-vinyl-3-ethyl pyrrolidinone, N'-vinyl-4,5-dimethyl pyrrolidinone,N-vinyl-5,5-dimethyl pyrrolidinone, N-vinyl-3,3,5-trimethylpyrrolidinone, N-vinyl-S-methyl-Scthyl pyrrolidinone,N-vinyl-3,4,5-trimethyl-3-ethyl pyrrolidinone,N-vinyl-6-methyl-2-piperidone, N-vinyl-6-ethyl-2-piperi-done,N-vi-nyl-3,S-dimethyl-Z-piperidone, N-vinyl-4,4-dimethyl-2- piperidone,N-vinyl-7-methyl caprolactam, N-vinyl-7-ethyll caprolactam,N-vinyl-3,5-dimethyl caprolactam, N-vinyl-4,6-dimethyl caprolactam,N-vinyl3,5,7-trimethyl caprolact-am.

The classes of catalysts which have been found effective in promotingthe polymerization of N-vinyl lactams include the oxides, hydroxides ofalkali metals and alkaline earth metals. Alkali metals and alkalineearth metals which may be mentioned include sodium, potassium, lithium,rubidium, cesium, calcium, magnesium, strontium and barium. Oxides,hydroxides and alkoxides of alkali and alkaline earth metals whichfunction as catalysts for the polymerization system include sodiumhydroxide, potassium hydroxide, barium hydroxide, calcium hydroxide,barium oxide, calcium oxide, and the like. Mixtures of oxides,hydroxides of different alkali and alkaline earth metals can also beemployed.

The amount of catalyst necessary to effect polymerization of the N-vinyllactam is not necessarily a critical feature of the invention and can bevaried over a wide range of from about .05 weight percent to 10.0 weightpercent, based on monomer, although amounts above and below this rangecan be employed if desired. An amount of catalyst of about 1.0 weightpercent provides an optimum of reaction rates and reaction times and istherefore preferred.

The first elevated temperature employed in carrying out the methods ofthe invention can be any elevated temperature and preferably atemperature in the range of from about 125 C. to 200 C.

The time at which the reaction mixture is held at the first elevatedtemperature to induce incipient polymerization can be variedconsiderably depending on the temperature employed. In general, however,the period of time will vary from about one hour or less to about threehours.

The second temperature at which the reaction mixture is maintained untilpolymerization is complete can be any temperature below the firstelevated temperature and generally, for the sake of convenience, ismaintained in the range of from 75 C. to 110 C. Polymerization of themixture is usually complete within a short time when maintained at atemperature in the above range.

In carrying out the methods of the invention, an N- vinyl lactam, suchas N-vinyl pyrrolidone, is charged to an autoclave equipped with astirrer, reflux condenser and thermometer. The reactants, lactam,catalyst and water are charged simultaneously, or, if desired, can beadded separately to the autoclave. The contents of the autoclave arepreferably purged with nitrogen gas or any other inert gas and thepressure on the reaction medium reduced and heat applied. The reactionmixture is maintained at the first elevated temperature for a period oftime sufficient to induce incipient polymerization after which it isallowed to cool to a second temperature lower than the first temperaturewhere it is maintained until a slight temperature rise is noted. Usuallythis slight temperature rise will occur within several minutes afterreaching the second elevated temperature. This second elevatedtemperature is maintained for an additional period of time, if desired,until polymerization is complete. Subsequently water is added to thereaction mixture and the mixture heated in order to extract any watersolubles from the polymer after which it is discharged, filtered anddried.

As used herein the term insoluble polyvinyl lactams and particularlyinsoluble polyvinyl pyrrolidone is intended to define the product whichis insoluble in water, strong mineral acids, caustic solutions andcommon organic solvents and to distinguish it from the soluble polymericmaterials based on N-vinyl pyrrolidone known in the art as representedby US. 2,265,450 and US. 2,335,- 454.

The following examples will serve to further illustrate the practice ofthe invention with greater particularity although it is to be understoodthat the invention is not limited thereto.

Example 1 To a one-gallon autoclave were charged 360 grams of N-vinylpyrrolidone, 3.6 grams of 50% aqueous sodium hydroxide and 52milliliters of distilled water. The charge was heated and maintained at140 C. for one hour, after which it was allowed to cool to 100 0., thenmaintained at that temperature. A rise of 6 C. was noted three minutesafter reaching 100 C. The mixture was held at 100 C. for one hour,cooled to 80 C., after which 1500 milliliters of water were added. Themixture was then heated and maintained at 100 C. for one hour in orderto extract any water solubles. The mixture was discharged as a whitepaste that filtered easily. There was provided insoluble polyvinylpyrrolidone in a yield of 97% of theory,

4 Example 2 To an autoclave were charged 360 grams of N-vinylpyrrolidone, 15 grams of 50% aqueous sodium hydroxide and milliliters ofdistilled water. The mixture was heated and maintained at C. for twohours, after which it was allowed to cool. At 75 C. the temperature rose7. There was provided insoluble polyvinyl pyrrolidone in a yield of 97%of theory.

Example 3 there was a rise of 4 C. At the same time, the agitatorj wasstopped due to the solidification of the mixture. Within thirty secondsthe mixture was completely polymerized, and the flask was packed tightlywith polymer.

There was provided insoluble polyvinyl pyrrolidone in a yield of 95% oftheory.

Example 4 To a small citrate type glass pressure flask were changed 36grams of N-vinyl pyrrolidone, 0.36 gram of 50% aqueous sodium hydroxideand 11 millliliters of water. A magnetic agitator was inserted, theflask was purged with nitrogen and sealed. The flask was heated in anoil bath while the contents were stirred magnetically. A temperature ofC. was maintained for two and a quarter hours, after which the oil bathwas allowed. to cool. The mixture did not polymerize until next dayafter remaining at room temperature for fourteen hours. There wasprovided insoluble polyvinyl pyrrolidone in a yield of 96% of theory.

Example 5 To a 500 gallon kettle were charged 500 pounds of N-vinylpyrrolidone, 5 pounds of 50% aqueous sodium hydroxide and 75 pounds ofwater. The mixture was heated and maintained at C. for two hours. It wasthen cooled over a one-hour period to 100 C. and maintained at thattemperature. After one-half hour at 100 C. the temperature rose to 125C. The mixture was treated as in Examples 1 and 2. There was providedinsoluble polyvinyl pyrrolidone in a yield of 96% o theory.

Example 6 T 0 an autoclave were charged 360 grams of N-vinylpyrrolidone, 5 grams of 50% aqueous potassium hydroxide and 51.5milliliters of distilled water. The charge was heated and maintained at140 C. for one hour, allowed to cool then maintained at 100 C. Afterone-half hour 1 at 100 C. a temperature rise of 8 C. was noted. Themixture was then treated as in Example 1. There was (BHzCH:

wherein each R is independently a member selected from the groupconsisting of hydrogen, methyl and ethyl, R represents a member of thegroup consisting of hydrogen and alkyl groups containing from 1 to 4carbon atoms and n represents a whole positive integer of from 2 through4 in the presence of a catalyst selected from the group consisting ofthe oxides and hydroxides of alkali metals and alkaline earth metals andwater in an amount of from 1.0 to 70 weight percent based on the weightof N-vinyl lactam at a first elevated temperature for a period of timesufficient to induce incipient polymerization and forthwith cooling saidmixture to a second temperature lower than said first temperature andmaintaining said mixture at said second temperature until polymerizaionis complete.

2. An improved method for the polymerization of N-vinyl lactams toproduce insoluble polymers thereof which comprises heating a mixturecomprising an N-vinyl lactam corresponding to the formula:

wherein each R is independently a member selected from the groupconsisting of hydrogen, methyl and ethyl, R represents a member of thegroup consisting of hydrogen and alkyl groups containing from 1 to 4carbon atoms and n represents a whole positive integer of from 2 through4 in the presence of a catalyst selected from the group consisting ofthe oxides and hydroxides of alkali metals and alkaline earth metals andwater in an amount of from about to 70 weight percent based on theweight of N-vinyl lactam at a first elevated temperature for a period oftime suificient to induce incipient polymerization and forthwith coolingsaid mixture to a second temperature lower than said first temperatureand maintaining said mixture at said second temperature untilpolymerization is complete.

3. The method according to claim 2 wherein the N-vinyl lactam is N-vinylpyrrolidone.

4. The method according to claim 2 wherein the N-vinyl lactam is N-vinylcaprolactam.

5. The method according to claim 2 wherein the N-vinyl lactam is N-vinylpiperidone.

6. The method according to claim 2 wherein the N-vinyl lactam isN-vinyl-S-methyl pyrrolidone.

7. The method according to claim 2 wherein the N-vinyl lactam isN-vinyl-7-methy1 caprolactam.

8. The method according to claim 2 wherein the catalyst is selected fromthe group consisting of sodium hydroxide, potassium hydroxide, bariumhydroxide, calcium hydroxide, barium oxide, calcium oxide, sodiumethylate and sodium methylate.

9. The method according to claim 2 wherein the N-vinyl lactam is N-vinylpyrrolidone and the catalyst is sodium hydroxide.

10. The method according to claim 2 wherein the N-vinyl lactam isN-vinyl pyrrolidone and the catalyst is potassium hydroxide.

11. The method according to claim 2 wherein the N-vinyl lactam isN-vinyl pyrrolidone and the catalyst is barium hydroxide.

12. The method according to claim 2 wherein the N-vinyl lactam isN-vinyl caprolactam and the catalyst is sodium hydroxide.

13. The method according to claim 2 wherein the N-vinyl lactam isN-vinyl piperidone and the catalyst is potassium hydroxide.

14. The method according to claim 2 wherein the N-vinyl lactam isN-vinyl-S-methyl pyrrolidone and the catalyst is potassium hydroxide.

15. The method according to claim 2 wherein the N-vinyl lactam isN-vinyl-7-methyl caprolactam and the catalyst is sodium hydroxide.

References Cited by the Examiner FOREIGN PATENTS 931,013 7/ 1963 GreatBritain.

JOSEPH L. SCHOFER, Primary Examiner.

W. HOOVER, Assistant Examiner.

1. AN IMPROVED METHOD FOR THE POLYMERIZATION OF N-VINYL LACTAMS TOPRODUCE INSOLUBLE POLYMERS THEREOF WHICH COMPRISES HEATING A MIXTURECOMPRISING AN N-VINYL LACTAM CORRESPONDING TO THE FORMULA: